Drop sensing unit



FIG. 1 is a top front perspective view of a drop sensing unit embodying my new design;

FIG. 2 is a left end elevation thereof;

FIG. 3 is a right end elevation thereof;

FIG. 4 is a rear elevation thereof;

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a top front perspective taken at a reduced scale.

The broken lines are shown for illustrative purposes only. 

The ornamental design for a drop sensing unit, as shown and described. 